> Recently, we have been thinking about
> how to improve the Wikibase interface,
> to get around its limitations - such as
> the lack of on-wiki queries. 

One other tool that seems like it would be worth including in the discussion there is LinkedWiki:
https://mediawiki.org/wiki/Extension:LinkedWiki
It can also create a table or a map from a SPARQL query, and related Lua functionally.

Regarding your proposal at the end, it reminds me of Cradle, which can use EntitySchemas to define types for creation; e.g. https://furry.wikibase.cloud/tools/cradle/?#/shex/E2
Perhaps it would be worth expanding that project to editing instead? The source is MIT-licensed:
https://github.com/magnusmanske/cradle

I agree it would be useful to have these tools more integrated into the UI itself, rather than as a constellation of clunky-looking add-ons.

-- 
Laurence 'GreenReaper' Parry - WikiFur.com